among the throngs of mourners flocking to johannesburg right now to bid farewell to nelson mandela are 91 heads of state, four united states presidents, tens of thousands of south africans and celebrities from all over the world. there will also be elite military troops, snipers and security dogs all there to watch over a stadium meant to hold some 90,000 people. they are coming to pay their respects and of course, celebrate mandela's life. anderson cooper is on the ground in johannesburg, where he caught up with bono. >> mandela also talked a lot about poverty which is obviously an issue very close to your heart. i think he said without the eradication of poverty, there can be no true freedom. >> yeah. overcoming poverty is not the gesture of charity, it's an act of justice. >> that's what you said. >> yes. like slavery, like apartheid, he said poverty is not natural. it is man-made and so it can be overcome by the actions of human beings. he said to some generations, for a chance to be great, you can be that great generation. i have been working for this man since i was a teenager, a